YES We show the termination of the TRS R: g(s(x)) -> f(x) f(|0|()) -> s(|0|()) f(s(x)) -> s(s(g(x))) g(|0|()) -> |0|() -- SCC decomposition. Consider the dependency pair problem (P, R), where P consists of p1: g#(s(x)) -> f#(x) p2: f#(s(x)) -> g#(x) and R consists of: r1: g(s(x)) -> f(x) r2: f(|0|()) -> s(|0|()) r3: f(s(x)) -> s(s(g(x))) r4: g(|0|()) -> |0|() The estimated dependency graph contains the following SCCs: {p1, p2} -- Reduction pair. Consider the dependency pair problem (P, R), where P consists of p1: g#(s(x)) -> f#(x) p2: f#(s(x)) -> g#(x) and R consists of: r1: g(s(x)) -> f(x) r2: f(|0|()) -> s(|0|()) r3: f(s(x)) -> s(s(g(x))) r4: g(|0|()) -> |0|() The set of usable rules consists of (no rules) Take the reduction pair: lexicographic combination of reduction pairs: 1. matrix interpretations: carrier: N^2 order: standard order interpretations: g#_A(x1) = ((0,1),(0,0)) x1 s_A(x1) = ((1,1),(1,1)) x1 + (1,1) f#_A(x1) = ((1,1),(0,0)) x1 2. matrix interpretations: carrier: N^2 order: standard order interpretations: g#_A(x1) = (3,3) s_A(x1) = ((1,1),(1,1)) x1 + (1,1) f#_A(x1) = ((1,1),(1,1)) x1 3. matrix interpretations: carrier: N^2 order: standard order interpretations: g#_A(x1) = (2,3) s_A(x1) = ((1,1),(1,1)) x1 + (1,1) f#_A(x1) = ((0,1),(1,1)) x1 The next rules are strictly ordered: p1, p2 We remove them from the problem. Then no dependency pair remains.